Treatment of a work piece by shot peening with granular media is an important finishing step in an increasing number of products as the benefits of doing so are becoming more well known. Controlling the peening flow rate for dispensing the peening media is important to provide predictable and repeatable results. In prior art peening systems, the flow rate of the media has been set with a fixed orifice sometimes with a mechanical or electrical valve. However, feedback to the controlling valve has not typically been provided by sensing the actual flow rate of media dispensed through the valve.
Often times the media used in peening is some type of ferrous metal. Spherically conditioned cut wire (SCCW) is often used due to its low cost and the wire is a steel product. Controlling ferrous metals can be done with a magnetic valve that when magnetized slows the fall of the metallic media through the valve. Sometimes, it is desirable to use non-metallic media such as glass beads or other ceramic material. In this case, a magnetic valve will serve no purpose in metering flow. Ideally a valve for non-ferrous media should be able to control the flow rate based on measuring the flow rate dispensed by a valve and then actuating the valve to achieve the desired flow rate.